prefixes nouns, adjectives or adjectival nouns for intensification; really; truly; totally; completely

a sperm whale

an adult son residing with his parents; generally has not yet or can not come into family inheritance / a female servant working in a daimyō, ōoku, or other high-ranking house

room rent

at-home clothes

(Internet slang) dirty room

真っ暗: total darkness

真っ暗: totally dark, pitch dark

まっかん蟹: coconut crab

(Classical Japanese, archaic, humble) to do; expresses humbleness / (Classical Japanese, archaic, polite) expresses politeness toward and distance from the listener